/*
 *  V4L2 video capture example
 *
 *  This program can be used and distributed without restrictions.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#include <getopt.h>             /* getopt_long() */

#include <fcntl.h>              /* low-level i/o */
#include <unistd.h>
#include <errno.h>
#include <malloc.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sys/ioctl.h>

#include <asm/types.h>          /* for videodev2.h */

#include <linux/videodev2.h>

#include <iostream>
#include <fstream>
#include <sstream>

using namespace std;

int i = 0;

#define CLEAR(x) memset (&(x), 0, sizeof (x))

struct buffer {
    void * start;
    size_t length;
};

static char * dev_name = NULL;
static int fd = -1;
struct buffer * buffers = NULL;
static unsigned int n_buffers = 0;

static void errno_exit(const char * s) {
    fprintf(stderr, "%s error %d, %s\n", s, errno, strerror(errno));

    exit(EXIT_FAILURE);
}

static int xioctl(int fd, int request, void * arg) {
    int r;

    do
        r = ioctl(fd, request, arg);
    while (-1 == r && EINTR == errno);

    return r;
}

static void process_image(const void * p) {
    ++i;
    fputc('.', stdout);
    fflush(stdout);

    std::stringstream out;
    out << "capt-" << i << ".raw";

    ofstream outfile(out.str().c_str(), ofstream::binary);
    outfile.write((const char*) p, buffers[0].length);
    outfile.close();
}

static int read_frame(void) {
    struct v4l2_buffer buf;

    CLEAR (buf);

    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buf.memory = V4L2_MEMORY_MMAP;

    if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf)) {
        switch (errno) {
        case EAGAIN:
            return 0;
        case EIO:
        default:
            errno_exit("VIDIOC_DQBUF");
        }
    }

    assert (buf.index < n_buffers);

    process_image(buffers[buf.index].start);

    if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
        errno_exit("VIDIOC_QBUF");

    return 1;
}

static void mainloop(void) {
    unsigned int count;

    count = 100;

    while (count-- > 0) {
        for (;;) {
            fd_set fds;
            struct timeval tv;
            int r;

            FD_ZERO (&fds);
            FD_SET (fd, &fds);

            /* Timeout. */
            tv.tv_sec = 2;
            tv.tv_usec = 0;

            r = select(fd + 1, &fds, NULL, NULL, &tv);

            if (-1 == r) {
                if (EINTR == errno)
                    continue;

                errno_exit("select");
            }

            if (0 == r) {
                fprintf(stderr, "select timeout\n");
                exit(EXIT_FAILURE);
            }

            if (read_frame())
                break;

            /* EAGAIN - continue select loop. */
        }
    }
}

static void start_capturing(void) {
    unsigned int i;
    enum v4l2_buf_type type;

    for (i = 0; i < n_buffers; ++i) {
        struct v4l2_buffer buf;

        CLEAR (buf);

        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        buf.index = i;

        if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
            errno_exit("VIDIOC_QBUF");
    }

    type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))
        errno_exit("VIDIOC_STREAMON");
}

static void uninit_device(void) {
    unsigned int i;

    for (i = 0; i < n_buffers; ++i)
        if (-1 == munmap(buffers[i].start, buffers[i].length))
            errno_exit("munmap");

    free(buffers);
}

static void init_mmap(void) {
    struct v4l2_requestbuffers req;

    CLEAR (req);

    req.count = 4;
    req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    req.memory = V4L2_MEMORY_MMAP;

    if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {
        if (EINVAL == errno) {
            fprintf(stderr, "%s does not support "
                "memory mapping\n", dev_name);
            exit(EXIT_FAILURE);
        } else {
            errno_exit("VIDIOC_REQBUFS");
        }
    }

    if (req.count < 2) {
        fprintf(stderr, "Insufficient buffer memory on %s\n", dev_name);
        exit(EXIT_FAILURE);
    }

    buffers = (buffer*) calloc(req.count, sizeof(*buffers));

    if (!buffers) {
        fprintf(stderr, "Out of memory\n");
        exit(EXIT_FAILURE);
    }

    for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {
        struct v4l2_buffer buf;

        CLEAR (buf);

        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        buf.index = n_buffers;

        if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf))
            errno_exit("VIDIOC_QUERYBUF");

        buffers[n_buffers].length = buf.length;
        buffers[n_buffers].start = mmap(NULL /* start anywhere */, buf.length,
                PROT_READ | PROT_WRITE /* required */,
                MAP_SHARED /* recommended */, fd, buf.m.offset);

        if (MAP_FAILED == buffers[n_buffers].start)
            errno_exit("mmap");
    }
}

static void init_device(void) {
    struct v4l2_capability cap;
    struct v4l2_cropcap cropcap;
    struct v4l2_crop crop;
    struct v4l2_format fmt;
    unsigned int min;

    if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap)) {
        if (EINVAL == errno) {
            fprintf(stderr, "%s is no V4L2 device\n", dev_name);
            exit(EXIT_FAILURE);
        } else {
            errno_exit("VIDIOC_QUERYCAP");
        }
    }

    if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
        fprintf(stderr, "%s is no video capture device\n", dev_name);
        exit(EXIT_FAILURE);
    }

    /* Select video input, video standard and tune here. */

    CLEAR (cropcap);

    cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    if (0 == xioctl(fd, VIDIOC_CROPCAP, &cropcap)) {
        crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        crop.c = cropcap.defrect; /* reset to default */

        if (-1 == xioctl(fd, VIDIOC_S_CROP, &crop)) {
            switch (errno) {
            case EINVAL:
                /* Cropping not supported. */
                break;
            default:
                /* Errors ignored. */
                break;
            }
        }
    } else {
        /* Errors ignored. */
    }

    CLEAR (fmt);

    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    fmt.fmt.pix.width = 640;
    fmt.fmt.pix.height = 480;
    fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
    fmt.fmt.pix.field = V4L2_FIELD_ANY;

    if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))
        errno_exit("VIDIOC_S_FMT");

    /* Note VIDIOC_S_FMT may change width and height. */

    /* Buggy driver paranoia. */
    min = fmt.fmt.pix.width * 2;
    if (fmt.fmt.pix.bytesperline < min)
        fmt.fmt.pix.bytesperline = min;
    min = fmt.fmt.pix.bytesperline * fmt.fmt.pix.height;
    if (fmt.fmt.pix.sizeimage < min)
        fmt.fmt.pix.sizeimage = min;

    init_mmap();

}

static void close_device(void) {
    if (-1 == close(fd))
        errno_exit("close");

    fd = -1;
}

static void open_device(void) {
    struct stat st;

    if (-1 == stat(dev_name, &st)) {
        fprintf(stderr, "Cannot identify '%s': %d, %s\n", dev_name, errno,
                strerror(errno));
        exit(EXIT_FAILURE);
    }

    if (!S_ISCHR (st.st_mode)) {
        fprintf(stderr, "%s is no device\n", dev_name);
        exit(EXIT_FAILURE);
    }

    fd = open(dev_name, O_RDWR /* required */| O_NONBLOCK, 0);

    if (-1 == fd) {
        fprintf(stderr, "Cannot open '%s': %d, %s\n", dev_name, errno,
                strerror(errno));
        exit(EXIT_FAILURE);
    }
}

int main(int argc, char ** argv) {
    dev_name = "/dev/video0";

    open_device();
    init_device();
    start_capturing();
    mainloop();
    uninit_device();
    close_device();
    exit(EXIT_SUCCESS);

    return 0;
}
